When Lew Ayres, who had played Dr. Kildare, was a conscientious objector during WWII and was black listed the studio (MGM) continued the lucrative series with Lionel Barrymore as Dr. Leonard B. Gillespie, Kildare's wheelchair bound mentor. Van Johnson was added as "Dr. Gillespie's New Assistant" (Dr. Randall 'Red' Adams) in the middle four below.

Brian A. Curran writes,

Obscure today. B-movies from the biggest studio, MGM. Lew Ayres, who played Dr. Kildare to Lionel Barrymore's Gillespie, was a pacifist and sought conscientious objector status during WW2. He ended up in a Civilian Public Service (CPS) camp until they let him enlist as a medic, where he rendered excellent service (later in the Pacific). During this period, when Ayres was unpopular, they made movies with just Gillespie. By war's end, Ayres was rehabilitated and he returned to films like "Johnny Belinda" and "Donovan's Brain."